IIT Kharagpur-led study says tropical rainforests could survive global warming

Tropical rainforests like the Amazon and Western Ghats, considered lungs of the planet, is likely to survive future global warming, according to a study led by Indian Institute of Technology, Kharagpur.

A release from the institution said that a team consisting of its scientists and also those from Calcutta University and University of Western Ontario studied detailed records of rainforests in sediments from Vastan coal mines of Gujarat deposited in coastal lagoons around 56 million years ago.

Coal layers in Vastan

The coal layers in Vastan are nothing but a spectacularly fossilised tropical rainforest containing a huge amount of plant and pollen remains as well as variety of mammals and insects that lived in these forests. India was a tropical island then, surrounded by oceans and Himalayas were yet to form. The period is known as Palaeocene-Eocene Thermal Maximum (PETM), when global carbon dioxide rose to an abnormally high level that the future global warming might reach.

“The study took several years of field and laboratory investigation. We had to date the sediments to confirm its PETM age and collected samples at centimetre intervals, analysed the pollens to understand how the tropical rainforest community evolved in response to such extreme global warming... The climate was also monitored by analysing oxygen isotopes in fossil teeth of small horse-like ungulate mammals that once roamed in these forests,” Prof. Anindya Sarkar, lead researcher of IIT Kharagpur, was quoted as saying in the release.

The study has just been published online in the Elsevierjournal, Global and Planetary Change. “We found a large anomaly in carbon isotopes exactly at 56 million years. This was such a characteristic signal for a super greenhouse globe with very high atmospheric carbon dioxide... The rainforest not only survived but also diversified during and after this global warming phase,” lead author of the paper, Arpita Samanta, a former PhD student at IIT Kharagpur and currently assistant professor at Kolkata’s Asutosh College, was quoted as saying.

How did the rainforest survive

Melinda K. Bera, a co-author and an isotope expert who developed the novel clay-based thermometer, said, “What helped the rainforest’s survival? We critically looked at the rainfall pattern and found that the warming intensified the rainfall and that possibly brought down the temperature. We call it rainfall-buffered temperature. The increased rainfall and lowered temperature sustained these ancient rainforests of western India.”

While scientists are divided on the issue, a 2023 report by the Intergovernmental Panel on Climate Change had warned that if the carbon dioxide emission and global warming continued unabated, the tropical rainforest community may altogether collapse much before the end of this century and would drive a global catastrophe affecting nearly 800 million people worldwide.